Contractor warrants for a period of (20) years after completion of installation that the materials installed by Contractor will be free of defects. Contractor warrants workmanship for a period of Three (3) years after completion of installation. This warranty does not cover problems due to ordinary wear and tear., abnormal severe weather, or other unusual disturbances of nature, abuse, modifications made by someone other then Contractor, or similar cause other than normal use of the products.